zener diode? ceramic capacitor? What is this?

Discussion in 'General Electronics Chat' started by ryanjohnlenz, Mar 18, 2015.

  1. ryanjohnlenz

    Thread Starter New Member

    Mar 18, 2015
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    Hi everyone-

    A bit out of my league here. Trying to figure out what this blue part is so that I can repair it--it's obviously been zapped (220 is a lot different than 120, it appears....).

    I thought maybe it was a ceramic capacitor, but the PCB board definitely shows a different symbol. A friend suggested a zener diode, but a quick image search showed nothing even close to this. Screen Shot 2015-03-18 at 6.41.16 PM.png Screen Shot 2015-03-18 at 6.41.39 PM.png
     
  2. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    It's a metal oxide varistor or MOV. They are used for surge protection.
     
  3. DickCappels

    Moderator

    Aug 21, 2008
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    There is an excellent chance that the things that components that the MOV was intended to protect are also damaged.
     
    Roderick Young likes this.
  4. ryanjohnlenz

    Thread Starter New Member

    Mar 18, 2015
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    Thanks, both of you. Spot on.

    Guess it's not much of a surge protector then, eh Dick? :)

    I'll fumble around with my multimeter and see if I can find any other damaged parts...
     
  5. wayneh

    Expert

    Sep 9, 2010
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    See F1? That's probably a fuse and it's likely blown. Was it on the back of the board or never installed?
     
  6. alfacliff

    Well-Known Member

    Dec 13, 2013
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    probably a lightning strike near. static dosnt usually smoke thm like that. probably not a direct hit with lightning, a lot more would have been burnt.
     
  7. Brevor

    Active Member

    Apr 9, 2011
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    The MOV is there for protection from voltage spikes. Your device should work without it. if not something else has been damaged.
     
  8. ryanjohnlenz

    Thread Starter New Member

    Mar 18, 2015
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    Well you guys are going to love this: Yes, there was fuse (F1) in there, which was blown from the first time the coffee grinder was plugged into 220 (instead of 110). I couldn't find a fuse, so I temporarily bypassed the fuse with an alligator clip (yes...I know...boy-genius here). Turns out the aligator clip must have also been bridging some other connection, because when I powered it up--poof, magic smoke.
     
  9. wayneh

    Expert

    Sep 9, 2010
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    Ah, the plot thickens as the smoke clears.
     
  10. ryanjohnlenz

    Thread Starter New Member

    Mar 18, 2015
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    :oops: Yes it was very exciting. My wife, feeling responsible for plugging it into 220v, even got to witness it. She's not an electrical whiz, but she did know enough to recognize that it was no longer her fault that the grinder may now be a very overpriced paperweight. Whoops.​
     
  11. PlasmaT

    Member

    Feb 19, 2015
    40
    6
    I do not think it was due any shorting of the alligator clips. Perhaps the MOV might have been rated just above 110V. But how did the other parts survive? :)
     
  12. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,515
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    This is one problem with MOV's they are often destroyed in the act of protecting the circuit, if tucked away out of site you may be not aware of it, and the next spike that comes along is not suppressed.
    It is usually a result of the MOV under rated or the energy of the surge voltage exceeds the MOV rating.
    Max.
     
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